Sunburn occurs when light (ultraviolet-ray) particularly in the ultraviolet region (200 to 400 nm), such as sunlight, artificial light, etc., attacks the skin. It has been said that sunburn is a cause of skin disorders such as erythema, blisters, burns and eventually skin cancer.
The ultraviolet-ray are classified to UV-A (wave A ultraviolet-ray; 320 to 400 nm), UV-B (wave B ultraviolet-ray; 280 to 320 nm), and UV-C (wave C ultraviolet-ray; 200 to 280 nm) depending on the wavelength region. Among these, UV-C is almost absorbed by the ozone layer before it reaches the surface of the earth, so most of the ultraviolet-rays reaching the ground are UV-A and UV-B. UV-A and UV-B have various effects on human skin, but the phenomenon which appears the most conspicuously is sunburn. Sunburn by UV-B is called sunburn which mainly causes inflammatory symptoms such as formation of erythema and blisters on the skin, etc., and sunburn by UV-A is called suntan which causes browning of the skin and induces an abrupt aging phenomenon by promoting lowering of elasticity of the skin and occurrence of wrinkles. It has also been known that UV-A promotes the initiation of erythema reaction, but this erythema response may be enhanced for some kinds of patients, thereby phototoxicity or photoallergic reaction may be caused in some cases.
Cosmetics such as sunscreen cream containing the ultraviolet-ray absorber have been commercially available to prevent such harmful effects by ultraviolet-ray. In order to avoid the damage caused by ultraviolet-ray, it is effective to properly select and use the ultraviolet-ray absorber depending on the purposes, and an UV-A absorbent and an UV-B absorbent are formulated by optionally selecting these in the conventional cosmetics. In recent years, cosmetics, etc., having higher ultraviolet-ray absorption property have been desired, and in view of such circumstances, the applicant of this application has also proposed an external composition for skin enhanced in ultraviolet-ray absorbability (Patent document 1). In such a situation, the external composition for skin which can further enhance the ultraviolet-ray absorbability has been required.